SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2dc39da58892d54a680572757e75b4edbd447dcf21f45dc74297c420b831eff3' 
  AND token = 'Dhyq/VzhPGvfYTfbjraWGNztmUIe79H6kDEbF+EnpMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}